Function of the Heater Core Temperature Sensor 4th Gen

[GTyankee]

I watched a video a few months back.
The vehicle was a Chrysler product.
The guy was going to do a Back Flush on the HVAC system.

After he back flushed the system, once or twice, then he used CLR
He was using too much air pressure

found that video

How To Unclog a Heater Core - EricTheCarGuy

Heater problems in the winter suck. But with a little diagnosis you can usually figure out the problem. Heater cores can get clogged from time to time and th...

www.youtube.com

 

[mtnrider]

I have a diesel but this is the method I used. It's worked for me several times.

Flushing A Heater Core

Come along with Eric O. at the SMA shop as we diagnose and repair this 2013 Ram 3500 Cummins that came in with a complaint of no heat out of the dash vents. ...

youtu.be

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[Jeepwalker]

CLR is a great product. We used it a lot to delime boiler heat exchangers. It works.

But boiler heat exchangers are made (usually) of S/S, brass/copper or Cast Iron. None of those are going to get 'eaten' up by CLR. Not easily. IDK how safe it's going to be in aluminum. It's not recommended. It probably won't "kill" it for a short period, but ...From the CLR site:
"We do not recommend using CLR on galvanized metal, aluminium, or copper. CLR will compromise these metals."

OP, If you have to take the heater box one more time, I would just bite the bullet and buy a new Mopar heater core for $200. I know money doesn't grow on trees, but your truck is 10 yrs old. Some owners have had leaks in just normal use in that time. Why risk the CLR (or age) from loosening braze joints, etc?? I wouldn't even buy an aftermarket H/C. Put any heater core possibilities behind you.

Note: I would probably flush the cooling system, drive it around with water in it for a day, then dump it and re-do it again with water (this time using distilled water - cheap at Walmart or Aldi's). Obviously don't start a hot engine with cold water in it. Repeat, then, flush again. The idea is to get all the floating garbage out of yer truck's cooling system before putting in a new heater core. Then re-do with the right coolant (with Mopar coolant & distilled water) before installing the new heater core. If you haven't done so already. Maybe you have. Run the truck a week before installing a new H/C.

Note 2: Our local Chrysler part dept sells coolant cheap out of their bulk barrels, and usually matches online Mopar parts pricing (sometimes they're $10-$12 more).

Just a thought.

 

[CM_Ram13]

I had used CLR on the original core before replacing it. I probably let it sit for 30 mins the first time, 2 hours the next 4 times, then replaced it. But I used CLR a couple weeks ago when flushing. I’m basing my thoughts on something away from the core since it was replaced last year with a mopar one and it didn’t fix the heat then. It seemed like the temp only went up a hair.

But it could be a defective one since I’ve heard many cases of that and changing it again could fix it entirely

 

[Marshall]

I did not read all the posts, but if you put a new one in, I would be looking at valves, blend doors and such, rubber hoses and ?????????????
I have a good multimeter with a temp probe on it. Handy as hell and it seems dead on.
It is a Greenlee, quite expensive new, but I picked it up at a dealer shop auction, not that I needed another meter , but WTH , like ammo, never can have too much.

I would have said a heater core plugged with dirt, crap , but as you put new on that is out .
Wifes Honda 2008 has a cabin filter and when we where still in the country, the mice thought that was a great place to build a condo.
But you will not have a cabin filter in 13?

 

[RamDiver]

I did not read all the posts, but if you put a new one in, I would be looking at valves, blend doors and such, rubber hoses and ?????????????
I have a good multimeter with a temp probe on it. Handy as hell and it seems dead on.
It is a Greenlee, quite expensive new, but I picked it up at a dealer shop auction, not that I needed another meter , but WTH , like ammo, never can have too much.

I would have said a heater core plugged with dirt, crap , but as you put new on that is out .
Wifes Honda 2008 has a cabin filter and when we where still in the country, the mice thought that was a great place to build a condo.
But you will not have a cabin filter in 13?

^^^^
This would be my approach too.

If the heater core has been replaced with an OEM HC, without any improvement, before I gamble that it may have been defective from new, I'd mechanically hot wire the blend doors to the best state for heat production, as a test.

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[Dusty]

^^^^
This would be my approach too.

If the heater core has been replaced with an OEM HC, without any improvement, before I gamble that it may have been defective from new, I'd mechanically hot wire the blend doors to the best state for heat production, as a test.

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Yes, because the one item yet to be discussed is the electronic control system.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 100953 miles.

 

[CM_Ram13]

I realized a couple days ago that the lower radiator hose spring seems to be rotted. I’m guessing when the core was changed that not all crap in the system was fully flushed and it clogged the core very quickly after being replaced. I’m going to dive in and replace everything besides the radiator Saturday - water pump, all hoses, coolant, core just to ensure it’s all fully cleaned out and new. All blend doors work 100% as they should. The fan motor is working fully, blows nice and hard at all temperatures.

 

[Sherman Bird]

I've been struggling getting heat in my '13 Ram 1500. Basically have checked and changed every single thing possible with the coolant and HVAC system besides change the radiator, thermostat, or water pump: they work just fine. I've always wondered the function of the heater core temp sensor (HCTS) though. Would this cause any temperature change in the cabin if it is not getting correct voltage, resistance, etc? Is there a fuse it is connected to? I've tried having it seated normally, unplugged, and keeping it plugged in while outside the HVAC housing - just hanging behind the glove box - with no difference in any scenario. Any help is appreciated.

Do you have EATC? (Electronic Automatic Temperature Control)

 

[GTyankee]

I do not understand a few things:

If the Thermostat is 185°F to 190°F, does that mean that the water in the hoses is the same temperature ?
If the water inside of the hoses does reach that temperature, where the hell does that heat disappear to after passing through 5 foot of hose ?
I can tell everyone, that the heat in my Ram, even when new, never came anywhere near that temperature, even with the Recirculation door closed.

Take a ride in a Ford truck that is 5 or more years old & you will not want to keep the heat turned up to full heat.

The same when it comes to the hottest part of the summer, our Rams do not really cool off the inside of the cab when the outside temperature is over 100 - 112°F plus

 

[RamDiver]

I do not understand a few things:

If the Thermostat is 185°F to 190°F, does that mean that the water in the hoses is the same temperature ?
If the water inside of the hoses does reach that temperature, where the hell does that heat disappear to after passing through 5 foot of hose ?
I can tell everyone, that the heat in my Ram, even when new, never came anywhere near that temperature, even with the Recirculation door closed.

Take a ride in a Ford truck that is 5 or more years old & you will not want to keep the heat turned up to full heat.

The same when it comes to the hottest part of the summer, our Rams do not really cool off the inside of the cab when the outside temperature is over 100 - 112°F plus

The temperature inside the hose better be close to the thermostat value, I'd guess within about 5° or 10° depending on the outside ambient but don't forget, we're measuring the temperature of the outside of the hose.

IIRC, I saw about 175°F where the hose goes through the firewall and into the heater core.
So maybe, the thermostat value less 15°?

I've read countless reports that describe poorly performing HVAC on Ram trucks, mine is not one of those.

It takes no effort to make it meat locker cold in the summer or blazing hot in the winter.
I have no idea why my Ram's HVAC is excellent and others are not.

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[CM_Ram13]

Do you have EATC? (Electronic Automatic Temperature Control)

This is the hvac control unit in my truck. I don’t believe there’s any EATC, only manual controls.

 

[mtnrider]

I do not understand a few things:

If the Thermostat is 185°F to 190°F, does that mean that the water in the hoses is the same temperature ?
If the water inside of the hoses does reach that temperature, where the hell does that heat disappear to after passing through 5 foot of hose ?

That rubber hose is a pretty good insulator.... The water itself is going to be in the 180-190 range.

 

[Sherman Bird]

So, I went into my service information. The manual HVAC is all they show for the 2013.
That said, there is no heater core temperature sensor shown, BUT, there is an evaporator core temperature sensor shown.

 

[GTyankee]

What is my HVAC system called

I only use the RECIRCULATION button in the image
everything is else i do on the radio screen
I don't even change the vents settings,
I just have 2 vents open on the dash, the ones on the passenger side are closed. No sits there, so i just closed them.

 

[Joseph Godvin]

Heater Core Plugged !!!

 

[Dusty]

The temperature inside the hose better be close to the thermostat value, I'd guess within about 5° or 10° depending on the outside ambient but don't forget, we're measuring the temperature of the outside of the hose.

IIRC, I saw about 175°F where the hose goes through the firewall and into the heater core.
So maybe, the thermostat value less 15°?

I've read countless reports that describe poorly performing HVAC on Ram trucks, mine is not one of those.

It takes no effort to make it meat locker cold in the summer or blazing hot in the winter.
I have no idea why my Ram's HVAC is excellent and others are not.

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There were complaints about HVAC issues soon after the 5th gens were released. They were not meeting the design specification. Ram issued a retrofit that essentially replaced the entire Heater/HVAC assembly (plus a software update). I've got a very early 2019 and mine has always met the factory specs. Quite by accident i think I may have stumbled on the root cause of the problem.

As far as heat issues go, I can't think of any complaints I've heard except this OP's.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 10109 miles.

 

[RamDiver]

There were complaints about HVAC issues soon after the 5th gens were released. They were not meeting the design specification. Ram issued a retrofit that essentially replaced the entire Heater/HVAC assembly (plus a software update). I've got a very early 2019 and mine has always met the factory specs. Quite by accident i think I may have stumbled on the root cause of the problem.

As far as heat issues go, I can't think of any complaints I've heard except this OP's.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 10109 miles.

That may explain why I thought there were HVAC issues but in reality, they were limited to a certain vintage of 5th gen trucks.

I've dealt with many poor cooling faults and I think they include 4 gen as well.

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[CM_Ram13]

I’m thinking it’s mostly something running through the coolant system that sometimes blocks the core. I was driving on the highway yesterday going about 80mph for half an hour with heat on - got inside air temp to 80°, still not hot but at least warm. Driving 50mph maybe 5 minutes, inside air temp 71°. Shut the truck off and got out for half an hour, then got back on the highway up to 90mph for 10 minutes, heat at 96° - actually HOT, had to open the window a bit. Then cooled again as I slowed and down to 70° on backroads. I didn’t change the hvac settings at all: fan speed on 2nd of 4 speed, full heat, blowing on face. Drive for approximately 2 hours total. Outside temp 35-38°.

Doesn’t always do that but seemed odd the higher the speed/rpm, the hotter the air temp out of the vents. Any different opinions with that info? I’m still going to change thermostat, water pump, core and fully flush everything this weekend.

All cold this morning - outside temp 21°, inside air blowing 52° on full heat.

 

[GTyankee]

Do you have the Fresh Air Door closed during your test runs ?